Calendar

Sep
20
Tue
Colloquium Thesis Proposal: Ethan Dederick
Sep 20 @ 3:00 pm – 4:00 pm
Colloquium Thesis Proposal: Ethan Dederick @ Science Hall 310

Utilizing Planetary Oscillations to Constrain the Interior Structure of the Jovian Planets

Ethan Dederick

Seismology has been the premier tool of study for understanding the
interior structure of the Earth, the Sun, and even other stars. Yet in this
thesis proposal, we wish to utilize these tools to understand the interior
structure of the Jovian planets, Saturn in particular. Recent observations
of spiral density structures in Saturn’s rings caused by its oscillations
have provided insight into which modes exist within Saturn and at what
frequencies. Utilizing these frequencies to compare to probable mode can-
didates calculated from Saturn models will also us to ascertain the interior
profiles of state variables such as density, sound speed, rotation, etc. Using
these profiles in a Saturn model, coupled with tweaking the interior struc-
ture of the model, i.e. the inclusion of stably stratified regions, should
allow us to explain which modes are responsible for the density structures
in the rings, as well as predict where to look to find more such structures.
In doing so, we will not only have a much greater understanding of Sat-
urn’s interior structure, but will have constructed a method that can also
be applied to Jupiter once observations of its mode frequencies become
available. In addition, we seek to explain if moist convection on Jupiter is
responsible for exciting its modes. We aim to do this by modeling Jupiter
as a 2D harmonic oscillator. By creating a resonance between moist con-
vective storms and Jovian modes, we hope to match the expected mode
energies and surface displacements of Jupiter’s oscillations.

Oct
17
Mon
Pizza Lunch: Caitlin Doughty
Oct 17 @ 12:30 pm – 1:30 pm
Pizza Lunch: Caitlin Doughty @ AY 119

Title: Probing the z~6 UVB with Aligned Metal Absorbers

Caitlin Doughty

 

Nov
11
Fri
Colloquium: Amy Simon (Host: Nancy Chanover)
Nov 11 @ 3:15 pm – 4:15 pm
Colloquium: Amy Simon (Host: Nancy Chanover) @ Biology Annex 102

Outer Planets Update

Dr. Amy Simon, NASA

The Hubble Outer Planet Atmospheres Legacy (OPAL) program is a yearly program for observing each of the outer planets over two full rotations. Observations began with Uranus in 2014, adding Neptune and Jupiter in 2015 (Saturn will be included in 2018, after the end of the Cassini mission). These observations have provided interesting new discoveries in their own right, but are also now being combined with observations from a number of facilities, including NASA’s IRTF, Keck, the VLA, as well as the Kepler and Spitzer missions to further expand the breadth of science they contain.  This talk will cover the latest observations for each of these planets and what we are learning from these data sets.

 

Nov
14
Mon
Pizza Lunch: Drew Chojnowski
Nov 14 @ 12:30 pm – 1:30 pm
Pizza Lunch: Drew Chojnowski @ AY 119

Title: H-band Spectral Variability of Classical Be Stars

Drew Chojnowski

 

Jan
30
Mon
Pizza Lunch: Caitlin Doughty
Jan 30 @ 12:30 pm – 1:30 pm
Pizza Lunch: Caitlin Doughty @ AY 119

Title: Effect of molecular gas on simulated C II, C IV absorber fractions (598 Talk)

Caitlin Doughty

 

Feb
24
Fri
Colloquium: Thomas Rivinius
Feb 24 @ 3:15 pm – 4:15 pm
Colloquium: Thomas Rivinius

Our Current Understanding of Classical Be Stars

Dr. Thomas Rivinius, Chile, ESO Paranal

I will introduce Be stars as B-type stars with gaseous disks in Keplerian rotation. These disks form by mass ejection from the star itself and their evolution is then governed by viscosity. The observables and their formation in the disk will be discussed, as well as what we know about the central stars: they are the most rapidly rotating non-degenerate stars, they are non-radial pulsators, and they do not show magnetic fields. The pulsation is clearly (phenomenologically) linked to the mass ejection, but the physical mechanism responsible for the ejection and disk formation is not known. Finally, I will discuss several open questions of broader interest, including the (possibly absent) chemical mixing of very rapid rotators and the unexpectedly large viscosity of Be star disks.

 

Mar
2
Thu
Colloquium: Jack Burns (Host: Nancy Chanover)
Mar 2 @ 3:15 pm – 4:15 pm
Colloquium: Jack Burns (Host: Nancy Chanover) @ Domenici Hall Room 106

Cosmology from the Moon: The Dark Ages Radio Explorer (DARE)

Dr. Jack Burns, University of Colorado Boulder

In the New Worlds, New Horizons in Astronomy & Astrophysics Decadal Survey, Cosmic Dawn was singled out as one of the top astrophysics priorities for this decade. Specifically, the Decadal report asked “when and how did the first galaxies form out of cold clumps of hydrogen gas and start to shine—when was our cosmic dawn?” It proposed “astronomers must now search the sky for these infant galaxies and find out how they behaved and interacted with their surroundings.” This is the science objective of DARE – to search for the first stars, galaxies, and black holes via their impact on the intergalactic medium (IGM) as measured by the highly redshifted 21-cm hyperfine transition of neutral hydrogen (HI). DARE will probe redshifts of 11-35 (Dark Ages to Cosmic Dawn) with observed HI frequencies of 40-120 MHz. DARE will observe expected spectral features in the global signal of HI that correspond to stellar ignition (Lyman-α from the first stars coupling with the HI hyperfine transition), X-ray heating/ionization of the IGM from the first accreting black holes, and the beginning of reionization (signal dominated by IGM ionization fraction). These observations will complement those expected from JWST, ALMA, and HERA. We propose to observe these spectral features with a broad-beam dipole antenna along with a wide-band receiver and digital spectrometer. We will place DARE in lunar orbit and take data only above the farside, a location known to be free of human-generated RFI and with a negligible ionosphere. In this talk, I will present the mission concept including initial results from an engineering prototypes which are designed to perform end-to-end validation of the instrument and our calibration techniques. I will also describe our signal extraction tool, using a Markov Chain Monte Carlo technique, which measures the parameterized spectral features in the presence of substantial Galactic and solar system foregrounds.

 

Mar
6
Mon
Pizza Lunch: F.X. Schmider
Mar 6 @ 12:30 pm – 1:30 pm
Pizza Lunch: F.X. Schmider

JIVE/JOVIAL, a network for Jupiter’s seismology and atmosphere dynamics

F.X. Schmider, Observatoire de la Cote d’Azur

Apr
7
Fri
Colloquium: Lauren Waszek (Host: Jason Jackiewicz)
Apr 7 @ 3:15 pm – 4:15 pm
Colloquium: Lauren Waszek (Host: Jason Jackiewicz) @ BX102

The growth of Earth’s inner core: a new technique to constrain seismic properties in its outermost layers

Dr. Lauren Waszek, Department of Physics, NMSU

The inner core displays a hemispherical difference in seismic velocity, attenuation, and anisotropy, which is well-established from seismic studies. Recent observations reveal increasingly complex and regional features. However, geodynamical models generally only attempt to explain the basic east-west asymmetry. Regional seismic features, such as depth-dependence anisotropy or variation in hemisphere boundaries, are difficult to reproduce and relatively poorly constrained by seismic data. Processes to generate these complex features are debated.

The structures of the inner core are suggested to be formed as the inner core grows over time. Thus, the most recently-formed outermost layers likely hold the key to understanding the geodynamical mechanisms generating the inner core properties. Current datasets of the uppermost inner core and inner core boundary are limited by uneven data coverage, however. In the very uppermost inner core, seismic waves arrive with similar travel times and interfere, making measurements difficult.

Despite the uneven coverage of current datasets, we can use them to infer a very slow inner core super-rotation. The first ever global tomographical inversion for the inner core allows us to make regional observations, and map the lateral variation in the hemispherical structures. In the uppermost inner core, we have developed a new waveform modeling technique with synthetic data to separate these seismic phases, allowing us to measure the seismic properties in the very uppermost inner core. This, in combination with geodynamical modeling, will help us determine how the inner core hemispheres and other features are generated.

 

 

 

 

 

 

Oct
16
Mon
Pizza Lunch: Ken Naiff
Oct 16 @ 12:30 pm – 1:30 pm
Pizza Lunch: Ken Naiff @ AY 119

Dark Sky Images

Ken Naiff

Ken, an retired engineer, is a highly technically skilled and artistic
astrophotographer.  He will be sharing some of his work and elaborating on
the technical methods and processing techniques he applies to obtain his
unique and enhanced images.  You can see Ken’s work at:

https://darkskyimagesbyken.com/products